Troubleshooting

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Troubleshooting

This section covers ways to help determine the cause when problems happen with DNS and BIND9.

Testing

resolv.conf

The first step in testing BIND9 is to add the nameserver's IP Address to a hosts resolver. The Primary nameserver should be configured as well as another host to double check things. Simply edit /etc/resolv.conf and add the following:


nameserver	192.168.1.10
nameserver	192.168.1.11


	You should also add the IP Address of the Secondary nameserver in case the Primary becomes unavailable.

ping

Once a host has been configured to use the new nameserver one of the simplest tests is the ping utility. From a terminal prompt enter:


ping example.com

This tests if the nameserver can resolve the name example.com to an IP Address. The command output should resemble:


PING example.com (192.168.1.10) 56(84) bytes of data.
64 bytes from ns (192.168.1.10): icmp_seq=1 ttl=64 time=0.800 ms
64 bytes from ns (192.168.1.10): icmp_seq=2 ttl=64 time=0.813 ms

dig

If you installed the dnsutils package you can test your setup using the DNS lookup utility dig:

After installing BIND9 use dig against the loopback interface to make sure it is listening on port 53. From a terminal prompt:
dig -x 127.0.0.1
You should see lines similar to the following in the command output:
;; Query time: 1 msec ;; SERVER: 192.168.1.10#53(192.168.1.10)
If you have configured BIND9 as a Caching nameserver "dig" an outside domain to check the query time:
dig ubuntu.com
Note the query time toward the end of the command output:
;; Query time: 49 msec
After a second dig there should be improvement:
;; Query time: 1 msec

named-checkzone

A great way to test your zone files is by using the named-checkzone utility installed with the bind9 package. This utility allows you to make sure the configuration is correct before restarting BIND9 and making the changes live.

To test our example Forward zone file enter the following from a command prompt:
named-checkzone example.com /etc/bind/db.example.com
If everything is configured correctly you should see output similar to:
zone example.com/IN: loaded serial 6 OK
Similarly, to test the Reverse zone file enter the following:
named-checkzone example.com /etc/bind/db.192
The output should be similar to:
zone example.com/IN: loaded serial 3 OK


	The Serial Number of your zone file will probably be different.

Logging

BIND9 has a wide variety of logging configuration options available. There are two main options. The channel option configures where logs go, and the the category option determines what information to log.

If no logging option is configured the default option is:


logging {
     category default { default_syslog; default_debug; };
     category unmatched { null; };
};

This section covers configuring BIND9 to send debug messages related to DNS queries to a separate file.

First, we need to configure a channel to specify which file to send the messages to. Edit /etc/bind/named.conf.local and add the following:
logging { channel query.log { file "/var/log/query.log"; severity debug 3; }; };
Next, configure a category to send all DNS queries to the query file:
logging { channel query.log { file "/var/log/query.log"; severity debug 3; }; category queries { query.log; }; };


	Note: the debug option can be set from 1 to 3. If a level isn't specified level 1 is the default.

Since the named daemon runs as the bind user the /var/log/query.log file must be created and the ownership changed:
sudo touch /var/log/query.log sudo chown bind /var/log/query.log
Before named daemon can write to the new log file the AppArmor profile must be updated. First, edit /etc/apparmor.d/usr.sbin.named and add:
/var/log/query.log w,
Next, reload the profile:
cat /etc/apparmor.d/usr.sbin.named | sudo apparmor_parser -r
For more information on AppArmor see the section called “AppArmor”
Now restart BIND9 for the changes to take affect:
sudo /etc/init.d/bind9 restart

You should see the file /var/log/query.log fill with query information. This is a simple example of the BIND9 logging options. For coverage of advanced options see the section called “More Information”.


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